You know Pluto still gets to be called Pluto, right? Just like Ceres will always be Ceres, even if it's number 1 in the list (it was the first asteroid discovered). In fact, they recently named the other dwarf planet that's just been known by a number (2003 UB313) and a nickname ("Xena") until now. It's now officially called Eris.
The other choice (which was proposed) would be to leave Pluto a planet, and make Ceres, Eris and Pluto's moon Charon planets too. Plus any other somewhat large iceballs we find out in the Kuiper Belt, which will probably number in the 10's or 100's once we find them all. Better to stick to 8 planets, I say.
Edit: Hilarious mneumonic device, Raerae!